We plan to continue work on the relationship of structure to the function of toxin. We are particularly interested in the mechanism by which the two chains separate within the cell. Modified toxins will be tested for chemotherapeutic activity. The mechanism of action of the plant toxins, ricin and abrin, will be further investigated. Biochemical properties of a number of human tumors grown in the athymic mouse will be determined. The synthesis and the study of properties of a number of carriers suitable for delivering drugs will be carried out with the hope of developing more specific anti-tumor agents.